From f0b9d31c6edd50a6207489cd1bd4ddac814b9cd2 Mon Sep 17 00:00:00 2001 From: Lu Baolu Date: Wed, 23 Jul 2025 15:20:45 +0800 Subject: [PATCH] iommu/vt-d: Fix UAF on sva unbind with pending IOPFs Commit 17fce9d2336d ("iommu/vt-d: Put iopf enablement in domain attach path") disables IOPF on device by removing the device from its IOMMU's IOPF queue when the last IOPF-capable domain is detached from the device. Unfortunately, it did this in a wrong place where there are still pending IOPFs. As a result, a use-after-free error is potentially triggered and eventually a kernel panic with a kernel trace similar to the following: refcount_t: underflow; use-after-free. WARNING: CPU: 3 PID: 313 at lib/refcount.c:28 refcount_warn_saturate+0xd8/0xe0 Workqueue: iopf_queue/dmar0-iopfq iommu_sva_handle_iopf Call Trace: iopf_free_group+0xe/0x20 process_one_work+0x197/0x3d0 worker_thread+0x23a/0x350 ? rescuer_thread+0x4a0/0x4a0 kthread+0xf8/0x230 ? finish_task_switch.isra.0+0x81/0x260 ? kthreads_online_cpu+0x110/0x110 ? kthreads_online_cpu+0x110/0x110 ret_from_fork+0x13b/0x170 ? kthreads_online_cpu+0x110/0x110 ret_from_fork_asm+0x11/0x20 ---[ end trace 0000000000000000 ]--- The intel_pasid_tear_down_entry() function is responsible for blocking hardware from generating new page faults and flushing all in-flight ones. Therefore, moving iopf_for_domain_remove() after this function should resolve this. Fixes: 17fce9d2336d ("iommu/vt-d: Put iopf enablement in domain attach path") Reported-by: Ethan Milon Closes: https://lore.kernel.org/r/e8b37f3e-8539-40d4-8993-43a1f3ffe5aa@eviden.com Suggested-by: Ethan Milon Signed-off-by: Lu Baolu Link: https://lore.kernel.org/r/20250723072045.1853328-1-baolu.lu@linux.intel.com Signed-off-by: Will Deacon --- drivers/iommu/intel/iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index d1791b50f7911..a4f53b62dfbb1 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -4081,8 +4081,8 @@ static int blocking_domain_set_dev_pasid(struct iommu_domain *domain, { struct device_domain_info *info = dev_iommu_priv_get(dev); - iopf_for_domain_remove(old, dev); intel_pasid_tear_down_entry(info->iommu, dev, pasid, false); + iopf_for_domain_remove(old, dev); domain_remove_dev_pasid(old, dev, pasid); return 0; -- 2.47.2